Regex DataAnnotations

Question

I am using the following Regular expression pattern

for Name filed vaidation in MVC5 Application

@"^[a-zA-z]+[(?<=\d\s]([a-zA-Z]+\s)*[a-zA-Z])+$"

1)Ram Anand           - Working fine

2)Ram                       - Not working

Please can you share the regex code for access the following

both validation

1)Alpha

2)Alpha Alpha

 

Thanks